The relatively sudden interest in the site is due largely to Microsoft's intent to beat Google in the advertising space, the insiders explained. After Google declared its intent to buy web ad agency DoubleClick this year, Microsoft promptly responded by purchasing rival group aQuantive in an attempt to gain a similar level of clout. Facebook has reportedly developed its own ad system that would float context-sensitive ads based on a member's profile and habits.

A decision by either Google or Microsoft to acquire a stake could also have an impact on their respective partners, as the control would encourage the victor to integrate some of its own features with Facebook's main services and its applications. Partners that rely heavily on their services could also be affected, such as Apple. The latter recently used Facebook's iPhone-optimized website to demonstrate web applications on the iPod touch during chief executive Steve Jobs' September iPod event, while also using several Google services such as Google Maps and YouTube on the touch as well as the iPhone.